Printing ribbon spools or cartridges which include a means for replenishing the ink drawn from a printing ribbon are well known in the art. Most typically, these reinking devices comprise an inking roller impregnated with ink which is pressed against a ribbon. Other ribbon spools have a liquid ink reservoir with a wick placed in contact with a ribbon.
Those spools or cartridges characterized by a roller mechanism include the reinking device disclosed in U.S. Pat. No. 4,653,947. Detailed therein is an endless ribbon cartridge used with newer computer printers and typewriters. The '947 947 device includes a rotatable pinch roller mounted on an inker case, a force ink-impregnated inking roller tangent to the pinch roller which is configured with a spring biasing mechanism to maintain a constant relation with the pinch roller. The inker case is pivotably mounted within the cartridge housing and the spring is biased such that the pinch roller mounted to the inker case is urged into frictional contact with the drive roller with the ribbon passing therebetween. Ink is passed to the ribbon as the ribbon is pulled between the pinch and ink rollers.
The '947 reinking cartridge is exemplary of roller type reinking devices of the prior art. All roller type devices are characterized by an ink-impregnated ribbon placed in a cartridge or on a spool. The ink is somewhat replenished as it is drawn past the ink roller. Most importantly, that portion of the ribbon in contact with the roller will become soaked with excessive ink because the ribbon is in continuous contact with the ink-impregnated roller all of the time, even when the printer is not in use. Consequently, characters printed for a time after the printer has restarted will be non-uniform (excessively dark), lowering the print quality of the document.
While forced ink roller-type cartridges are configured to avoid leakage, each possesses the following disadvantages. Initially, a provision must be made in the cartridge for the ink-impregnated roller. The ink roller performs no function other than to ink the ribbon, and is therefore a source of extra cost. Secondly, there must be included a spring mechanism and an opposing roller to urge the ink roller against the ribbon. There must also be a provision in the cartridge to interface the reinking ribbon mechanism with the remainder of the cartridge. All of the above lead to increased cost and complexity.
Furthermore, the roller type reinking cartridges have a finite shelf life, since the reinking roller begins to dry as soon as the cartridge leaves the factory. Lastly, there is no control over the amount of ink which is provided to the ribbon. When the inking cartridge is fresh an unnecessary large quantity of ink will be provided to the ribbon and, as the cartridge ages, the ribbon will provide an undesirably small quantity of ink.
It would be advantageous for a ribbon cartridge device to provide a continuous self-inking of the ribbon. This device should not be susceptible to leakage and should be easily adapted for use in a variety of cartridge type printing machines. The present invention is directed towards such a ribbon cartridge.